feature #6233 Document translation_domain for choice fields (merorafael, WouterJ)

This PR was merged into the 2.7 branch.

Discussion
----------

Document translation_domain for choice fields

It has a slightly different behaviour, I think it's interested to document it.

This finishes #5614.

| Q | A
| --- | ---
| Doc fix? | no
| New docs? | yes
| Applies to | 2.7+
| Fixed tickets | -

Commits
-------

4b92e88 Document translation_domain setting for choice fields
92998d8 translation_domain doc fix
2fa2386 choice_translation_domain doc fix
3ad5111 Travis fix
5957927 Update entity.rst

Author: xabbuh

reference/forms/types/choice.rst

@@ -17,6 +17,7 @@ To use this field, you must specify *either* ``choices`` or ``choice_loader`` op
 |             | - `choice_loader`_                                                           |
 |             | - `choice_label`_                                                            |
 |             | - `choice_attr`_                                                             |
+|             | - `choice_translation_domain`_                                               |
 |             | - `placeholder`_                                                             |
 |             | - `expanded`_                                                                |
 |             | - `multiple`_                                                                |
@@ -41,6 +42,7 @@ To use this field, you must specify *either* ``choices`` or ``choice_loader`` op
 |             | - `mapped`_                                                                  |
 |             | - `read_only`_                                                               |
 |             | - `required`_                                                                |
+|             | - `translation_domain`_                                                      |
 +-------------+------------------------------------------------------------------------------+
 | Parent type | :doc:`form </reference/forms/types/form>`                                    |
 +-------------+------------------------------------------------------------------------------+
@@ -348,6 +350,8 @@ type:
 
 .. include:: /reference/forms/types/options/required.rst.inc
 
+.. include:: /reference/forms/types/options/choice_type_translation_domain.rst.inc
+
 Field Variables
 ---------------
 

reference/forms/types/entity.rst

@@ -24,6 +24,7 @@ objects from the database.
 | options     |                                                                  |
 |             | - `placeholder`_                                                 |
 |             | - `choice_translation_domain`_                                   |
+|             | - `translation_domain`_                                          |
 |             | - `expanded`_                                                    |
 |             | - `multiple`_                                                    |
 |             | - `preferred_choices`_                                           |
@@ -176,7 +177,6 @@ em
 If specified, this entity manager will be used to load the choices
 instead of the ``default`` entity manager.
 
-
 Overridden Options
 ------------------
 
@@ -199,6 +199,8 @@ type:
 
 .. include:: /reference/forms/types/options/choice_translation_domain.rst.inc
 
+.. include:: /reference/forms/types/options/choice_type_translation_domain.rst.inc
+
 .. include:: /reference/forms/types/options/expanded.rst.inc
 
 .. include:: /reference/forms/types/options/multiple.rst.inc

reference/forms/types/options/choice_type_translation_domain.rst.inc

@@ -0,0 +1,8 @@
+translation_domain
+~~~~~~~~~~~~~~~~~~
+
+**type**: ``string`` **default**: ``messages``
+
+In case `choice_translation_domain`_ is set to ``true`` or ``null``, this
+configures the exact translation domain that will be used for any labels or
+options that are rendered for this field